Hi,
While searching for something else, I discovered a 2MB 127 page
.pdf file which is full of useful reference info about electronics,
components and things related to electronics, with a lot of handy
charts etc. Well worth the 2MB download, I thought.
It's at www.elfa.se/en/fakta.pdf

That's a remarkable reference Bob - apart from all the crap I manage to
consistently forget, it has sections on stuff that I kind of wondered about,
but have never got around to looking up - a good example of that is the
section on plastics.

That's what I thought too. Also the meanings of all those approval
marks, plus everything from pneumatic symbols to microprocessor basics
and ASCII codes and even valves (tubes). It's amazing to find it all
in a single well-written document. :-)